The present invention relates to a process for the production of bonded zeolite bodies.
Zeolites have unique adsorption properties and catalytic activities, and, therefore, recently they have been widely used in separation processes such as separation of p-xylene from C.sub.8 aromatic hydrocarbons and separation of nitrogen from air, and catalytic processes such as disproportionation of toluene.
For general utility in commercial adsorption or catalytic processes, the zeolites are usually formed into the bonded bodies using binding agents.
Heretobefore, the bonded zeolite bodies have been commonly produced by the following process. The zeolite in powder form is kneaded with a binding agent and water, and then is shaped by means of extrusion or other granulating apparatus into the required form. The granules thus obtained are then dried and calcined. As binding agents in this field, clay mineral or other noncrystalline inorganic materials have been proposed, for example, kaolin, bentonite, attapulgite (U.S. Pat. No. 2,973,327), sodium silicate (British Pat. No. 982,872) and silica sol (British Pat. No. 974,643).
It is also known that some organic materials are used together with inorganic binding agents to improve the crush strength or attrition resistance of zeolite bodies. For example, combinations of attapulgite and stearic acid (U.S. Pat. No. 2,973,327), kaolin and lignosulfonate (U.S. Pat. No. 3,219,590), and kaolin and carboxymethylcellulose (Japanese Pat. Publication No. 32,572/1971) have been proposed.
In such a known process, the use of noncrystalline inorganic materials is required and, therefore, the obtained zeolite bodies contain therein at least 10%, usually 20-30%, by weight of noncrystalline inorganic materials. Needless to say, the inorganic binders have such disadvantages that they decrease the zeolite content in the bonded zeolite body and the adsorptive or catalytic efficiency of the zeolite is reduced proportionately.